There have been suggested a disk apparatus and others for recording a result of imaging using a high-capacity recording medium capable of random access, such as an optical disk.
With relation to such a disk apparatus, for instance, Japanese Patent Laid-open No. 2001-84705 suggests a method of improving the operation of a large number of files by using an index file that is created from the large number of files recorded in a recording medium and recorded in the recording medium.
Japanese Patent Publication No. 2002-278996 suggests another method of further improving the operation of the large number of files by managing each file layered in the index file created as described above.
Namely, in these methods, the index file is formed by grouping extracted information containing information concerning the managed files extracted with respect to each attribute, and each group is formed with a sequence of entries based on the extracted information from each file. More specifically, these index files are configured with a text entry assigned with the extracted information by a letter string concerning a disk title and each managed file, a thumbnail image entry assigned with the extracted information by a still image (thumbnail image) showing the content of the disk title and each managed file, and a property entry assigned with data indicating the attribute of the disk title and each managed file.
This enables the index file, for instance, to provide a user with a thumbnail image of each file from the thumbnail image entry and to provide the user with a title of each file from the text entry so as to select a desired file easily and reliably.
Since the property entry has various information concerning corresponding files therein, it is assumed to be possible, in such an index file, to refine a file recorded in the recording medium by searching based on the creation date of the file using the records in the property entry to search the desired file quickly. Since the text entry has the title recorded therein, it is also assumed to be possible to search the desired file quickly by searching each of the text entries by keyword searches. It is also supposed to be possible to refine the files and search the desired file easily and reliably by searching the thumbnail image entry depending on whether there is a thumbnail image or not.
However, in searching a file recorded in such a recording medium, when a large number of files are recorded in the recording medium, it is possible that the same searches are often repeated. It is also possible that a search processing is executed to further refine the result of a search executed in the past. It is supposed to be useful to make effective use of the result of the search result in the past at a later date.